• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Taxonomic note
Following Kennedy and Spencer (2014) the genus Phalacrocorax has been divided into six genera, with P. magellanicus, P. bougainvilliorum, P. atriceps, P. verrucosus, P. carunculatus, P. chalconotus, P. onslowi, P. campbelli, P. ranfurlyi and P. colensoi moved into Leucocarbo (HBW and BirdLife International 2018).

Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Handbook of the Birds of the World and BirdLife International. 2018. Handbook of the Birds of the World and BirdLife International digital checklist of the birds of the world. Version 3. Available at: https://datazone.birdlife.org/userfiles/file/Species/Taxonomy/HBW-BirdLife_Checklist_v3_Nov18.zip.
Kennedy, Martyn & Spencer, Hamish. 2014. Classification of the Cormorants of the World. Molecular phylogenetics and evolution. 79: 249-257.
Turbott, E.G. 1990. Checklist of the Birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
A2bcde+3bcde+4bcde	A2bcde+3bcde+4bcde; B2ab(ii,iii,iv,v); C2a(ii)	A2bcde+3bcde+4bcde; B1ab(ii,iii,iv,v)+2ab(ii,iii,iv,v); C2a(i,ii); D1+2

Red List history

Year	Category	Criteria
2018	Critically Endangered	A2bcde+3bcde+4bcde
2016	Critically Endangered	A2bcde+3bcde+4bcde
2012	Critically Endangered	B2ab(ii,iii,iv,v)
2010	Critically Endangered	B2a+b(ii,iii,iv,v)
2009	Critically Endangered	B2a+b(ii,iii,iv,v)
2008	Critically Endangered
2007	Critically Endangered
2005	Critically Endangered
2004	Endangered
2000	Endangered
1996	Vulnerable
1994	Vulnerable
1988	Lower Risk/Least Concern

Migratory status	not a migrant	Forest dependency	does not normally occur in forest
Land-mass type		Average mass	-

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	8,600 km2	poor
Area of Occupancy (breeding/resident)	1 km2	good
Number of locations	2	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	710 mature individuals	good	estimated	2011
Population trend	decreasing	poor	suspected	2006-2030
Rate of change over the past 10 years/3 generations (longer of the two periods)	90-99%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	90-99%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	90-99%	-	-	-
Generation length	8.7 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: A census carried out in 2011 counted 355 breeding pairs (Debski et al. 2012), presumably equating to 714 mature individuals and c.1,070 individuals in total.

Trend justification:  Debski et al. (2012) estimated a 58% decline from 1997 to 2012. 

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
New Zealand	extant	native		yes

Country/Territory	IBA Name
New Zealand	Chatham Islands (nearshore)
New Zealand	Main Chatham
New Zealand	Mangere
New Zealand	Rangiauria Pitt Island
New Zealand	Star Keys Motuhope
New Zealand	Tuku

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Marine Coastal/Supratidal	Sea Cliffs and Rocky Offshore Islands	major	breeding
Marine Intertidal	Rocky Shoreline	major	breeding
Marine Intertidal	Tidepools	major	breeding
Marine Neritic	Macroalgal/Kelp	major	resident
Marine Neritic	Pelagic	suitable	resident
Marine Neritic	Seagrass (Submerged)	major	resident
Marine Neritic	Subtidal Loose Rock/pebble/gravel	major	resident
Marine Neritic	Subtidal Rock and Rocky Reefs	major	resident
Marine Neritic	Subtidal Sandy	major	resident
Marine Neritic	Subtidal Sandy-Mud	major	resident
Altitude		Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Biological resource use	Fishing & harvesting aquatic resources - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Biological resource use	Hunting & trapping terrestrial animals - Persecution/control	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Climate change & severe weather	Habitat shifting & alteration	Timing		Scope		Severity		Impact
		Future		Whole (>90%)		Unknown		Unknown
		Stresses Indirect ecosystem effects, Ecosystem degradation
Human intrusions & disturbance	Recreational activities	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species disturbance, Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Bos taurus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Canis familiaris	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Felis catus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Gallirallus australis	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Ovis aries	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Sus domesticus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Trichosurus vulpecula	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Arctocephalus forsteri	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Reduced reproductive success

Purpose	Scale
Pets/display animals, horticulture	international

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Recommended citation
BirdLife International (2024) Species factsheet: Chatham Islands Shag Leucocarbo onslowi. Downloaded from https://datazone.birdlife.org/species/factsheet/chatham-islands-shag-leucocarbo-onslowi on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 23/11/2024.